Esters are a class of organic compounds that are derived from an acid (organic or inorganic) in which at least one hydroxyl group (-OH) is replaced by an alkyl (alkoxy) group (-O-alkyl) . In other words, esters are compounds that are formed by bonding an alcohol group with a group of organic acids, by losing water molecules. Esters are widespread in nature and are widely used in industry. In nature, fats are, in general, triesters derived from glycerol and fatty acids. Esters are responsible for the aroma of many fruits, including apples, durians, pears, bananas, pineapples, and strawberries. Several billion kilograms of polyesters are produced industrially annually, important products being polyethylene terephthalate, acrylate esters, and cellulose acetate.

Esterification is the general name for a chemical reaction in which two reactants (typically an alcohol and an acid) form an ester as the reaction product. Esters are common in organic chemistry and biological materials, and often have a pleasant characteristic, fruity odor. This leads to their extensive use in the fragrance and flavor industry. Esters are also found in many polymers.

Some key properties of esters include:

• Boiling Point: Small esters have boiling points which are similar to those of aldehydes and ketones with the same number of carbon atoms. Esters, like aldehydes and ketones, are polar molecules and so have dipole-dipole interactions as well as van der Waals dispersion forces. However, they do not form ester-ester hydrogen bonds, so their boiling points are significantly lower than those of an acid with the same number of carbon atoms/Esters/Properties_of_Esters).

• Odor: Many esters have distinctive fruit-like odors, and many occur naturally in the essential oils of plants. This has also led to their common use in artificial flavorings and fragrances which aim to mimic those odors.

• Solubility: Carboxylic acid esters of low molecular weight are colorless, volatile liquids with pleasant odors, slightly soluble in water. Certain volatile esters are used as solvents for lacquers, paints, and varnishes; for this purpose, large quantities of ethyl acetate and butyl acetate are commercially produced.

Overall, esters are important compounds with a wide range of applications in industry and nature.